Made glorious by Wayne's World, it was done in the movie to show a boner coming on (ie: near the total babe Cassandra). Can also just be an exclamaition of happiness. It's important to do the pelvic thrust with it though...Basically, the sweetest word ever with the greatest action.
*Attractive person walks in* "Sha-wing!"
"Here's $20" "sha-wing"
by Hilary October 5, 2004
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It's the noise of thrusting your hard penis at a pretty girl.

The art of thrusting one's pelvis towards a hot chick and saying, "Schwing!" as if one had a hard wanker.
youtube.com/watch?v=szkgylvDYA4&NR=1
Waynes World Sha-wing
by Orang Utan October 15, 2011
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